2001 Jeep Cherokee Brake Lights

Tiny
JAMIEKITT
  • MEMBER
  • 2001 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 115,000 MILES
Brake Lights come on when headlights or marker lights are on. When brakes are applied with headlights off, digital odometer readout & radio readout dim. Brakes are working normally. No warning lights are on. Tried replacing stop light switch-no help. Checked all bulbs & wiring to rear lights-lookls OK. Any ideas?
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Friday, March 5th, 2010 AT 9:10 AM

3 Replies

Tiny
CARADIODOC
  • EXPERT
First, if you have a trailer wiring harness, check if it's chewed up and the wires are shorted. One common symptom is the radio display dimming. It has a circuit tied to the tail lights to tell the display to dim when the running lights are on. If you have a U-Haul-installed trailer harness with three red leds in the plug, it used to be common for them to short causing the same symptoms.

If that doesn't look like the problem, there could be a dealer / factory-installed adapter harness that you may be able to remove as a test.

Another common cause used to be using the wrong marker / tail light bulb. Single terminal on the bottom instead of the twin terminal that was needed. Newer vehicles use a flat, plastic-base bulb that this won't happen to. I think that's what you have. This problem applied to the older round, brass-base bulbs.

If none of these solve the problem, search for "beef99". He is a Jeep specialist and may have additional thoughts.

Caradiodoc
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Friday, March 5th, 2010 AT 10:04 AM
Tiny
JAMIEKITT
  • MEMBER
I did have an after market trailer wiring harness installed, but I removed it & it made no difference. Bulbs haven't been replaced recently(this problem just started within the past week), And I checked them all, anyway, thinking maybe the parking light filiment had somehow shorted accross to the brake light(both are in the same bulb). How do I search for "beef99"?
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Friday, March 5th, 2010 AT 10:47 AM
Tiny
CARADIODOC
  • EXPERT
Next, unplug the tail lamp housings from the vehicle's wiring harness. If the radio display still dims when the brake pedal is pressed, the problem has to be in the vehicle. In particular, look for a buildup of corrosion between two adjacent pins in a connector, especially along the frame or inside the body.

If the problem is gone, plug one housing back in, then see what happens when you press the brake pedal. If the problem comes back when plugging in one of them, that's the one to look at for the problem.

By the way, I found a similar problem on a friend's son's Chevy truck not too long ago. One of the buttons of solder, (the contact) on the base of the bulb, broke off and was stuck between the right front turn signal terminal and the running light terminal right next to it in the socket. We didn't see it rght away because of the grease in the socket. His left signal worked fine but the right signal blinked real fast and caused all the running / tail lights to turn on, and the radio display flickered.

I put in a call to the administrators to contact beef99 on your behalf. I don't know how to reach him either through the forum unless he's online. Hopefully he will have some more ideas.

Caradiodoc
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Friday, March 12th, 2010 AT 3:12 PM

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